Chemical reagent



252. COMPOSITIONS,

Patented Feb. 11, mo

UNITED STATES Examim;

PATENT OFFICE FRED H. RHODES, OF ITHACA, NEW YORK CHEMICAL REAGENT No Drawing. Application filed July 18,

The invention relates to inhibitors or restrainers useful in chemical and electrochemical processes for preventing or retarding the evolution of hydrogen at the surfaces of metals immersed in the solution or for otherwise preventing or retarding the chemical action of acids on metals. The invention is particularly applicable to chemical processes wherein metals such as iron, steel, nickel, etc., are subjected to themf aci s for removing scale, rust or oxide from the surfaces thereof. Such processes are often referred to as pickling processes and are widely used in manufacturing establishments.

My invention consists in the discovery of a series of chemical compounds which when added to certain chemical reagents act to inhibit the undesired reactions of said reagents without interfering with the desired reactions thereof. For instance when added to a pickling bath of a composition that would ordinarily have a corrosive action upon metals, such compounds serve to retard the corrosive action on the metals and the consequent evolution of hydrogen without interfering materially with the desired function ofdissolving the oxide, rust or scale found on the surface of the metal.

There are many advantages in the use of a pickling bath having incorporated therein an inhibitin agent for retarding the chemlcal action of the acid on the metal. For example, such a composition is useful in removing the layer of iron oxide which is formed on steel or iron during the rolling of sheets, the drawing of wires or rods, the spinning of thin shapes and the annealing of shapes prior to an application of a coating of vitreous enamel, glass, tin, zinc, or other metal or paint, varnish enamel, lacquer or other protective or decorative coating. Another use of the process is in the removing of the metallic oxide or carbonate forming on copper or other non-ferrous materials. Another advantageous use is in eliminating the scale forming in pipes and in the tubes of automobile radiators which often seriously interferes with the proper flow and circulation of the fluid through the radiator. My in- 1929. Serial N0. 379,818.

vention is applicable generally to the removal of oxides and scales from metals by a pickling process and the use of the inhibiting agents not only prevents or diminishes the attack of the metals themselves by the acid but also creates more healthful working conditions surrounding the pickling bath. The evolution of hydrogen gas, which is an incident of the attack of the metal by the acid, results in the carrying into the surrounding air of a certain amount of the acid of the bath in the form of a spray which is injurious to the operators and wasteful of the acid material.

In its broader aspects, my invention contemplates the use of the inhibiting agents hereinafter more fully described in connection with any chemical or electrochemical solution or reagent which under normal conditions of operation will evolve hydrogen at the surface of a metal immersed therein. In other words, my invention provides a means for causing desired chemical or electrochemical reactions to take place and without substantially decreasing the rate of said reactions causing; an inhibiting action retarding 'or actually preventing the evolution of hydro gen which would normally take place without the presence of the inhibiting agents.

As a further example of the utility of my invention, it may sometimes be found desirable to use the new inhibiting agents in connection with electroplating processes. It is well known that in the electrodeposition of certain metals hydrogen is liberated at the 35 cathode in addition to the metal which it is desired to plate. By using the inhibiting agents in accordance with my invention the evolution of hydrogen at the cathode may be retarded without correspondingly retarding the deposition of the metal. Thus the efficiency of the plating process is increased and certain undesirable characteristics of the plated metal caused by the evolution of hydrogen may be eliminated.

The new inhibiting agents forming the subject matter of this application may be broadly classified Wm and I have found t at in general the derivatives of acridine having the more complex 'molecules are much better inhibitors than acridine itself. While there are a large num- .ber of compounds coming within the purview of this invention, I will refer more specifically to some of the more important compounds with which I have made careful tests to determine the degree of inhibiting power possessed thereby.

The following substances are examples of compounds which have been tested and found to have markedly superior inhibiting properties to acridine itself:

Methylacridine C H; N Phenylacrldine &

3,6-dimethy1-2,7-diethyl diaminoacridine hydrochloride H=C CH:

CIHIHN NHCzHa 3,6-diaminoacridine 3,6H1imethyl-2,7 diaminoacridine ethylchloride H 0 CH8 The compounds mentioned above may ordinarily be used as inhibiting agents in the pure state or in the relatively impure form resulting from commercial methods of manufacturing the same. It has been found that in many cases the impure compounds are more efficient inhibitors than the chemically pure substances. This may possibly be due to the presence of small amounts of more complex derivatives in the impure material. The inhibiting compounds may be introduced into the chemical reagent not only in the form of a free base as indicated in some of the formulas given above, but may also be used in the form of a salt, as, for example, the hydrochlorideof the base.

The amount of the inhibiting agent to be used for any given chemical solution depends not only upon the efficiency of the inhibiting agent but also on operating conditions and the exact results desired in the particular phenylacridine is added to a pickling bath containing 7.5% sulphuric acid there is an inhibiting action of the acid on iron to the extent of 97.5% at 60 C. when the phenylacridine is present in the proportion of 10 millimols per liter of solution.

It has also been found that 3% of phosphine RN added to a 7 solution of sulp uiid'zfcid will give 98% inhibition. The compound known as phosphine RN is a brown powder and is the hydrochloride of an organic base derived from acridine and containing two methyl groups and two ethylamino groups substituted on the acridine nucleus. This compound probably has the structural formula denoted by the name 3, 6 dimethyl-2, 7 diethyl diaminoacridine hydrochloride; Y'

The amount of inhibiting action may vary for different manufacturing conditions. For example, in pickling thin sheet steel for light enameled ware it is desirable to use suflicient inhibitor to effect as much as 98% inhibition, whereas in pickling thicker sheets for heavy enamel as little as inhibition might be desired. Thus according to my invention, the inhibiting agent may be added in amounts suflicient only to retard the evolution of hydrogen or on the other hand a suitable inhibiting agent of high etficiency may be added in larger amounts in order to substantially prevent the evolution of hydrogen.

From the above description it will be noted that my invention relates to the discovery of a series of cyclic organic nitrogen compounds having inhibiting characteristics rendermg them very valuable in chemical and electrochemical processes with which they have never heretofore been associated. While I have described certain compounds and certain processes with particularity, it is to be understood that the invention is not necessarily limited thereby except in the light of the claims appended hereto.

What I claim as my invention is:

1. The process of inhibiting or restraining the evolution of hydrogen at the surface of a metal immersed in a liquid reagent which consists in introducing into the liquid reagent a derivative of acridine which contains a univalent substituent attached to a carbon atom of the acridine nucleus.

2. The process of inhibiting or restraining the evolution of hydrogen at the surface 252. COMPOSITIONS,

of a metal immersed in a liquid reagent which consists in introducing into the liquid reagent a derivative of acridine which contains a unvalent organic radical attached to the carbon atom of the acridine nucleus.

3. The process of inhibiting or restraining the evolution of hydrogen at the surface of a metal immersed in a liquid reagent which consists in introducing into the liquid reagent a derivative of acridine which contains at least one hydrocarbon radical attached to the carbon atom of the acridine nucleus.

4. The process of inhibiting or restraining the evolution of hydrogen at the surface of a metal immersed in a liquid reagent which consists in introducing into the liquid reagent a derivative of acridine which contains at least one alkyl radical attached to the carbon atom of the acridine nucleus.

5. The process of inhibiting or restraining the evolution of hydrogen at the surface of a. metal immersed in a liquid reagent which consists in introducing into the liquid regaent a derivative of acridine which contains at least one methyl radical attached to the carbon atom of the acridine nucleus.

6. The process of inhibiting or restraining the evolution of hydrogen at the surface of a metal immersed in a liquid reagent which consists in introducing into the liquid reagent a derivative of acridine which contains at least one methyl group.

7. The process of inhibiting or restraining the evolution of hydrogen at the surface of a metal immersed in a liquid reagent which consists in introducing into the liquid reagent 3.6 dimethyl 2.7 diethyl diamino acridine.

8. The process of inhibiting or restraining the evolution of hydrogen at the surface of a metal immersed in a liquid reagent which consists in introducing into the liquid reagent 3.6 dimethy12.7 diethyl diamino acridine hydrochloride.

9. The process of inhibiting or restraining the evolution of hydrogen at the surface of a metal immersed in a liquid reagent which consists in introducing into the liquid reagent the material known as phosphine RN, a brown powder which is the hydrochloride of an organic base derived from acridine and containing two methyl groups and two ethylamino groups substituted in the acridine nucleus.

10. A liquid bath for chemical or electrochemical purposes comprising a solution which under normal conditions of operation evolves hydrogen at the surface of a metal immersed therein and an inhibitor or restrainer in said solution for diminishing the evolution of hydrogen comprising a derivative of acridine which contains a univalent substituent attached to a carbon atom of the acridine nucleus.

11. A liquid bath for chemical or electro- Examine chemical purposes comprising a solution which under normal conditions of operation evolves hydrogen at the surface of a metal immersed therein and an inhibitor or restrainer in said solution for diminishing the evolution of hydrogen comprising a derivative of acridine which contains the univalent organic radical attached to the carbon atom of the acridine nucleus.

12. A liquid bath for chemical or electrochemical purposes comprising a solution which under normal conditions of operation evolves hydrogen at the surface of a metal immersed therein and an inhibitor or restrainer in said solution for diminishing the evolution of hydrogen comprising a derivative of acridine which contains at least one hydrocarbon radical attached to the carbon atom of the acridine nucleus.

13. A liquid bath for chemical or electrochemical purposes comprising a solution which under normal conditions of operation evolves hydrogen at the surface of a metal immersed therein and an inhibitor or restrainer in said solution for diminishing the evolution of hydrogen comprising a derivative of acridine which contains at least one alykyl radical attached to the carbon atom of the acridine nucleus.

14. A liquid bath for chemical or electrochemical purposes comprising a solution which under normal conditions of operation evolves hydrogen at the surface of a metal immersed therein and an inhibitor or restrainer in said solution for diminishing the evolution of hydrogen comprising a derivative of acridine which contains at least one methyl radical attached to the carbon atom of the acridine nucleus.

15. A liquid bath for chemical or electrochemical purposes comprising a solution which under normal conditions of operation evolves hydrogen at the surface of a metal immersed therein and an inhibitor or restrainer in said solution for diminishing the evolution of hydrogen comprising a derivative of acridine which contains at least one methyl group.

16. A liquid bath for chemical or electrochemical purposes comprising a solution which under normal conditions of operation evolves hydrogen at the surface of a metal immersed therein and an inhibitor or restrainer in said solution for diminishing the evolution of hydrogen comprising 3.6 dimethyl 2.7 diethyl diamino acridine.

17. A liquid bath for chemical or electrochemical purposes comprising a solution. which under normal conditions of operation evolves hydrogen at the surface of a metal immersed therein and an inhibitor or restrainer in said solution for diminishing the evolution of hydrogen comprising 3.6 dimethyl 2.7 diethyl diamino acridine hydrochloride.

18. A liquid bath for chemical or electrochemical purposes comprising a solution which under normal conditions of operation 4 evolves hydrogen at the surface of a metal immersed therein and aninhibitor or restrainer in said solution for diminishing the evolution of hydrogen comprising the material known as phosphine RN, a brown powder which i the hydrochloride of an organic base derived from acridine and containing two methyl groups and two ethylamino groups substituted in the acridine nucleus.

In testimony whereof I aflix my signature.

FRED H. RHODES. 

